Regge cuts: A general approach

Abstract

We discuss an approach to the calculation of Regge-cut contributions to scattering amplitudes which relies only on the general structure of the physical Reggeon couplings. It thus allows a unified treatment of disparate models (such as the Feynman (Mandelstam) graph model and the dual model) and a general derivation of the Abramovskii--Gribov--Kancheli (AGK) rules. The structure of the Reggeon couplings is expressed through integrals over complex helicity. The Regge-cut amplitude can then be obtained, and its s-channel discontinuity, taken; there results a direct derivation of a set of ''cutting rules'' which express the total discontinuity as a sum of terms involving various discontinuities of the Reggeon couplings. The equality of these discontinuities follows directly if the singularities in complex helicity are the usual ones. Thus the AGK rules are seen to be quite model independent. Here we study in detail the simplest example: the Reggeon-particle cut in the four-particle amplitude. (AIP)